Research on contagious H5N1 viruses: Space suits needed?

Mar 6, 2012 (CIDRAP News) – Using the highest level of safety precautions for research on H5N1 viruses that can spread in mammals may slow the advance of science, but it's worth it in view of the grave risks involved, say some commentators writing today in mBio, a journal of the American Society for Microbiology (ASM).

But another commentator writing in the same journal says that using the strictest precautions, biosafety level 4 (BSL-4), would encumber research without making the work any safer than doing it in enhanced BSL-3 conditions, the next highest safety level.

The debate was sparked by the current controversy over whether two studies involving lab-derived H5N1 viruses that spread in ferrets via respiratory droplets should be published in full or edited to remove details that could allow others to generate the viruses.

In December, the National Science Advisory Board for Biosecurity (NSABB) took the latter course, out of a concern that bioterrorists or other malefactors could exploit the information. A heated debate among scientists, public health officials, biosecurity experts, and others has raged ever since.

The two journals involved, Science and Nature, have said they are willing to go along with the NSABB recommendation if a way can be found to provide the crucial details to scientists with a legitimate need for them.

Science intends to publish a study by Ron Fouchier, PhD, and colleagues of Erasmus Medical Center in the Netherlands. Using a combination of genetic engineering and passaging through ferrets, they generated an H5N1 virus that spread from ferret to ferret without direct contact. Accounts of the virus's lethality have differed somewhat, but apparently it was lethal to ferrets at least with deliberate tracheal inoculation at high doses.

Nature is looking to publish a study led by Yoshihiro Kawaoka, DVM, PhD, of the University of Wisconsin, Madison. His team combined the hemagglutinin from an H5N1 virus with other genes from an H1N1 virus and found that the hybrid could spread in ferrets via respiratory droplets, though it did not kill any of them.

Ferrets are generally considered the best animal models for how flu behaves in humans. Since the case-fatality rate (CFR) for confirmed human H5N1 cases is about 59%, the studies have raised the concern that unleashing a virus with increased human transmissibility could lead to a catastrophic pandemic.

The Fouchier and Kawaoka studies were conducted in "BSL-3 enhanced" conditions. BSL-3 is intended for pathogens that cause serious or potentially fatal disease and spread by the respiratory route, though vaccines or treatments may be available. Safety features include such things as controlled access, entry through an airlock, decontamination of all waste and lab clothing, use of biosafety cabinets when manipulating agents, and negative air flow into the lab.

BSL-4 precautions are intended for aeorosol-transmitted agents that often cause fatal illness and for which there are no vaccines or treatments. Workers in BSL-3 labs must either wear a pressurized suit or else work in a Class III biosafety cabinet, among many other precautions. The facility must be a separate building or an isolated zone of a building, with dedicated ventilation and decontamination systems.

Playing it safeSounding the call for a cautious approach to further research on H5N1 viruses with increased transmissibility are Michael J. Imperiale, PhD, and Michael G. Hanna III, MPH, both of the University of Michigan. The two serve on the university's Institutional Biosafety Committee, and Imperiale is an NSABB member but is expressing only his own views.

They note that the manual Biosafety in Microbiolgoical and Biomedical Laboratories (BMBL), provided by the Department of Health and Human Services (HHS), recommends using BSL-3 containment for highly pathogenic avian influenza viruses. However, making the H5N1 virus more transmissible changes its safety profile, they contend.

"While acknowledging that the ferret is indeed an experiment model [for human flu], we must assume that it is a valid model and therefore that this virus would spread similarly to other pandemic strains in history," they write.

Also, despite some recent debate over the true human CFR for H5N1 and whether many mild or asymptomatic cases have been missed, they say it is best to assume that "a large percentage" of people would not survive the infection.

Further, although HHS has stockpiled an H5N1 vaccine for pandemic preparations, Imperiale and Hanna assert that vaccination of researchers is not a likely option: "To date, a vaccine against H5N1 avian influenza virus has not been available, ruling out immunization of laboratory workers or the general public."

Although H5N1 responds to existing antiviral drugs, it is reasonable to assume that a more transmissible version of it would outrun the capacity of the public health system, and that in a pandemic, it would develop antiviral resistance, they add.

"Overall, then, we believe that the newly derived H5N1 HPAI [highly pathogenic avian influenza] virus should be handled at the highest biocontainment level, BSL4," they state.

They allow that they could be wrong in their assumptions about the validity of the ferret model and the high H5N1 fatality rate, but add, "In the meantime, why not follow the precautionary principle?"

A fairly similar case is made in an mBio letter by Lisa N. Murillo of the Theoretical Biology and Physics Group at Los Alamos National Laboratory in New Mexico.

On the question of ferrets as lab substitutes for humans, she asserts, "An avian virus that has recently been made ferret transmissible is probably quite close to being transmissible among humans, in terms of the number of additional mutations required, if it does not already have all of the required mutations."

However, she suggests requiring BSL-4 containment for Fouchier's virus only: "Because the Kawaoka lab viruses contain only the hemagglutinin of the avian H5N1 and did not cause any deaths among the ferrets studied, perhaps the Kawaoka lab viruses need not be handled at BSL-4." She advocates the "path of caution" for the Fouchier virus, saying the consequences of its accidental escape could be catastrophic.

BSL-3 deemed safe enoughIn another commentary, Adolfo Garcia-Sastre, PhD, of the Global Health and Emerging Pathogens Institute at Mount Sinai School of Medicine in New York City makes the case for using BSL-3 containment for research on the Fouchier and Kawaoka viruses.

While granting that humans need to be protected from exposure, he contends that ferret-adapted viruses "probably have attenuated infectivity and pathogenesis for humans." He suggests that "infection of laboratory personnel can be prevented by the use of powered air purifying respirators. These practices correspond to enhanced biosafety level 3, as described in the BMBL manual."

Garcia-Sastre also argues that the effects of any accidental exposure to the virus in an enhanced BSL-3 facility can be minimized by giving lab workers an H5N1 vaccine and antiviral drugs. He adds that the existence of a vaccine and antivirals argue against BSL-4 containment, since that level is intended for agents for which no vaccines or drugs are available.

"The use of BSL4 containment would not decrease the risk of virus release any more than enhanced BSL3 containment, but it would result in an unnecessary burden that would restrict research on H5N1 influenza transmission to a few facilities and considerably decrease the speed of research on this important pathogen," he concludes.

Acknowledging the tradeoffIn an accompanying mBio editorial, Arturo Casadevall, MD, PhD, the journal's editor-in-chief, cites pros and cons for both BSL-3 and BSL-4. Like Imperiale, he is an NSABB member but notes that he is not speaking for the board or for the ASM.

Casadevall notes that one country—Canada—has already moved to require BSL-4 precautions for research on mammalian-transmissible H5N1 viruses.

This step would "theoretically" make society safer but would simultaneously pose risks, "since critical experimental work will not get done simply because BSL4 facilities are few in number and already engaged in research with numerous other pathogens," he writes.

In addition, requiring the highest level of biosafety could affect vaccine production, because vaccine makers may not have the necessary facilities or may choose not to take vaccine projects under such restrictions, Casadevall writes.

"No matter what choices are made regarding containment level, we urge that great consideration be given to protecting the influenza research enterprise, since increased knowledge is critical for the defense against future pandemics," he adds.

The international dimensionAnother expert, James W. LeDuc, PhD, director of Galveston National Laboratory at the University of Texas Medical Branch in Galveston, said the two commentaries and editorial all make valid points, but he suggested that the authors should have paid more attention to the international aspects of lab biosafety.

"I read these commentaries quickly, but it seems to me that there is a distinct absence of the international aspect of the problem, which I find troubling," LeDuc told CIDRAP News via e-mail.

Seconding Casadevall's point about the tradeoff between safety and research progress, LeDuc said that requiring BSL-4 containment means that "many excellent scientists from around the world that might otherwise contribute to resolving the many challenges associated with this virus will be excluded."

He commented further that many new BSL-3 and BSL-4 labs have been built in recent years in countries where H5N1 has been found and are a source of great national pride.

"Once the engineered virus is published in the scientific literature, it's realistic to assume that scientists in these new labs might request access to the viruses to further research," LeDuc said. "Should these viruses be shared with them? What criteria will be used to ensure the safety and the security of the facilities, especially in areas where a culture and tradition of biosafety and biosecurity may not be well established?"

Referring to past lab exposures and accidents, such as during the SARS outbreak in 2003, he added, "These seem to me to be the more practical questions that have so far not been well addressed."